What is the law if only one of these was fulfilled (the Nesek did not spread, and it is deeper than the skin, or it spread, and it is not deeper than the skin)?
Da'as Zekenim citing Bechor Shor 1 : He is Tahor, like R. Yonason, who says (Bava Metzi'a 94b) that the prefix 'Vov' implies even one (unless it says 'together'). According to R. Yoshiyah, who says that Vov implies both of them, [he is Tamei].
Bechor Shor said so on verse 37, but he did not say whom the Halachah follows.
Rashi infers from "Lo Pasah" that if it spread, he is Tamei. Why is this needed? "V'Hinei Pasah" and "v'Im Pasoh Yifseh" (verses 36,35) teach that spreading is Metamei at the end the first or second week, or after Petur (being declared Tahor)!